The present invention relates to a digital photographing device, a method of controlling the digital photographing device, and a computer-readable storage medium storing a computer program that controls the digital photographing device.
Automatic photographing functions that provide high-quality images, in which photographing settings are not set by a user but automatically calculated, have been widely used in digital photographing devices. For this, a variety of algorithms to automatically calculate photographing settings have been developed.
When photographing settings for the automatic photographing are set, the degree of motion of a subject may be considered. When a moving subject is photographed, the subject may appear blurry in a created image file, and thus an exposure time is reduced. However, the amount of light is reduced due to the reduced exposure time, and thus sensitivity of an image pickup device may be increased. Thus, a digital photographing device may determine shutter speed and/or sensitivity of an image pickup device according to the degree of motion of the subject.
The shutter speed is a value determining an exposure time of an image pickup device, and may be set by time units. As the shutter speed decreases, the exposure time of the image pickup device decreases, and the amount of light incident onto the image pickup device decreases.
The sensitivity of the image pickup device is a value representing the degree of amplification of an electrical signal generated by the incident light by the image pickup device. The sensitivity of the image pickup device may be set using, for example, an ISO value. As the ISO value increases, the sensitivity of the image pickup device increases, and thus the subject may be photographed using a small amount of light. However, since overly sensitive photographing amplifies not only the signal generated by the incident light but also noise, image quality may be deteriorated.
A motion vector may be used to detect the degree of motion of a subject. The motion vector represents the motion of the subject according to time as a vector based on a block unit. Using the motion vector, the degree of motion of the subject may be estimated. For example, if motion vectors of each of the blocks are zero, it is estimated that there is no motion. If motion vectors of all blocks move in the same direction, it is estimated that the body of the digital photographing device is moving. In addition, if motion vectors of several blocks are large, it is estimated that a portion of the image is moving.
However, since the estimation of the degree of motion using the motion vector is based on block units, the photographing settings may not be precisely controlled. Furthermore, while the motion vector exhibits high reliability for edges, the motion vector cannot accurately show the degree of motion of the subject on edge-free portions, for example, on a desk, the floor, the ground, a wall, etc. As a result, overly sensitive photographing may be performed by calculating the degree of motion of the subject higher than that of the real motion, or the subject may appear blurry in a created image file by calculating the degree of motion of the subject lower than that of the real motion.